The P/C switch applies a ground signal to TCU pin C11 in the POWER position. I haven't traced it out any further since I hard-wired that switch permanently to the POWER position a long time ago.
Renix supplies voltage to C11 of the TCU in the Power mode.
Therefore, if your 7.5 amp "trans" fuse is blown, you will be stuck in comfort mode and have no reverse lights.